The missing pyramid of an obscure pharaoh that ruled Egypt 4,300 years ago could lie at the intersection of a series of invisible lines in South Saqqara, according to new astronomical and topographical research.

Connecting the funerary complexes raised by the kings of the 6th Dynasty between 2322 B.C. and 2151 B.C., these lines would have governed the sacred space of the Saqqara area, in accordance with a number of criteria such as dynastic lineage, religion and astronomical alignment.

"We are talking of meridian and diagonal alignments, with pyramids raised at their intersections. The only missing piece in this sort of grid is the pyramid of Userkare," Giulio Magli, professor of archaeoastronomy at Milan's Polytechnic University, told Discovery News. His research will appear in the next issue of the journal Mediterranean Archaeology and Archaeometry.

Known only from the king lists, Userkare was the second pharaoh of the 6th Dynasty and ruled briefly between Teti and Teti's son Pepi I. He took power after Teti was murdered, perhaps in a conspiracy he himself had maneuvered.

Little is known about this shadowy pharaoh.

"When Pepi I took control a few years later, Userkare disappeared from history. Finding his tomb might help understand those obscure years. The walls in his burial might also contain intact copies of the Pyramid Texts," Magli said, referring to the oldest known religious texts in the world that were carved on the walls and sarcophagi of the pyramids at Saqqara during the 5th and 6th Dynasties of the Old Kingdom.

Magli's hunt for the lost pharaoh evolved around previous studies on the pyramids of the Old Kingdom. Indeed, from the Step Pyramid of Djoser (second king of the 3rd Dynasty) to the now-collapsed pyramid of Unas (the last king of the 5th Dynasty), all these monuments appear to be connected by a pattern of diagonal invisible lines.

"Diagonal axes — generally oriented northeast by southwest — governed Giza, Abusir and the Saqqara central field. But we have a different pattern with some 6th dynasty kings: their funerary monuments in South Saqqara appear to have been planned according to meridian, north-south axes," Magli said.

8 real-life mummiesAccording to this pattern, the pyramid top of Pepi I (third king of the 6th Dynasty) aligned with that of Userkaf (first king of the 5th Dynasty), while the pyramid apex of Merenre (fourth king of the 6th Dynasty) aligned with that of Unas (last king of the 5th Dynasty).

"It is difficult to think that this rigorous meridian structure is just a coincidence. However something does not match in this pattern: no pyramid aligned with the Step Pyramid of Djoser, by far the most important and revered pyramid at Saqqara," Magli said.

The position was allegedly free, but the pharaohs chose different, sometimes more complex sites. For example, Pepi II, the third king of the 6th Dynasty, moved further to the southwest, and aligned the top of his pyramid with that of 3rd Dynasty King Sekhemkhet.

"There could be a simple explanation: the position in meridian alignment with the Step Pyramid was not free at all, being occupied by Userkare's complex," Magli said.

He suggested that Userkare's tomb is located approximately in the middle of the line connecting Pepi I and Merenre's diagonals, in alignment with Djoser's pyramid.

According to Egyptologist Vassil Dobrev, at the French Institute of Archaeology in Cairo, the suggestion makes sense on the satellite map, but is difficult to see on the field. Dobrev believes Userkare's tomb lie on a different, north-south diagonal in South Saqqara which would chronologically link the 6th Dynasty kings.

Indeed, he is excavating a 15-hectare area in Tabbet al-Guesh, where he has found several graves of priests from the 6th Dynasty.

Since the presence of a necropolis is a strong hint to a pyramid nearby, Dobrev believes Userkare's lies just there.

"These priests come to this place to serve the cult of a dead king. We do not have the name of Userkare yet, because the priests speak systematically about the 'King, their God.' They obviously refer to the dead king, [of] whom everybody knew the name," Dobrev told Discovery News.

According to Magli, the hidden structure may rather turn out to be a double-tomb complex.

"Apparently, a similar, 5th Dynasty double structure — not a pyramid — exists in Abusir. However, I'm confident Userkare's tomb will come to light in South Saqqara. Future excavations will solve the riddle," Magli said.